Electric valve circuit



Emacmuc VALVE cmcun Filed Aug. 2, 1941 4 e 9 9 5 /o 0 29 a 8 Inventor: Lysle W. Morton,

by JV Hi Attorney.

Patented Nov. 7, 1944 1 UNITED STATES. PATENT Y orrice ELECTRIC VALVE CIRCUIT LysleW. Morton, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application August 2, 1941, Serial No. 405,217

9 Claims.

My invention relates to electric valve circuits and more particularly to control or excitation circuits for electric valve means of the type employing an ionizable medium such as a gas or a vapor.

In electric valve translating circuits which employ electric valve apparatus of the type comprising an ionizable medium, it is important in many instances to employ excitation circuits which render the electric valve means conducting or conductive at a predetermined time during cycles of voltage of an associated alternating current supply circuit, and which are equally as precise in maintaining the electric valve means nonconductive during other predetermined intervals of time. In accordance with the teachings of my invention described hereinafter, I provide new and improved control or excitation circuits wherein both of these results are effected in a highly satisfactory manner.-

It is an object of my invention to provide a also prevents the occurrence of arc-backsduring those intervals of time in which it is desired to maintain the electric discharge device nonconducting.

For a better understanding of my invention,

reference may be had to the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims. trates an-embodiment of my invention as applied to a bi-phase rectifier, and Fig. 2 represents cernew and improved electric valve translating cirprotective system for excitation circuits of the' nature of that disclosed and claimed in United States Letters Patent No. 2,248,600, granted July 8, 1941, upon an application -Ernst'F. W. Alexanderson et al., and which is assigned to the assignee of the present application. More particularly,- the protective system which I provide relates to a system in which an electric discharge device of the immersion-ignitor control type also includes a control electrode or control bafile mounted Within the vicinity of the anode and on which is impressed a voltage of substantially the same wave form as that produced by the excitation circuit. The excitation circuit produces a periodic voltage of peaked wave form having positive'portions of substantially greater magnitude and shorter duration than the negative portions. Inthis manner, the auxiliary electrode or bafile not only assists in the establishment of an arc discharge between the cathode and the anode but tain operating characteristics thereof.

Referring now to Fig. 1 of the drawing, I have there represented my invention diagrammatically as applied to a system for energizing a direct current load circuit i from an alternating cur rent supply circuit 2 through electric translating apparatus including a transformer 3 and a pair of electric discharge devices 4 and 5. The electric discharge devices 4 and 5 are of the type comprising an ionizable medium, such as a gas or a vapor, and each includes an anode 6, an ionizable self-reconstructing type cathode such as a mercury pool cathode I, an immersion-ignitor control member 8 and an auxiliary baffle or con-" trol electrode 9 mounted within the vicinity of the anode 6. The immersion-ignitor control member is preferably constructed of a material such as boron-carbide or silicon-carbide having an electrical resistivity which is large compared with that of the associated mercury pool and effects the generation of a cathode spot on the cathode by the transmission, through the control member, of a predetermined minimum critical value of current. Each of the electric discharge devices A and 5 includes a transfer or relieving anode II] which serves to relieve the duty imposed on the associated control member 8 .by the transfer of the excitation current as soon as an arc discharge is established within the electric discharge device. I

I employ excitation circuits II and I2 of the type disclosed and claimed in the above-identifled Alexanderson et al. patent. The excitation circuits II and I2 generate periodic voltages of peaked wave form whereby precise initiations of arc discharges within the electric discharge devices 4 and 5 are obtained. The excitation circuits'more specifically include saturable inductive devices l3 and I4 having variable impedance Fig. 1 diagrammatically illusmagnitude and phase of the voltage of peaked wave form produced by the excitation circuits II and I2. Excitation circuits H and I2 also include serially connected resistances 2i, 22 and inductances 23 and 24. The inductances 23 and 24 provide a short circuit path for the direct current component of voltage which would otherwise appear across the immersion-ignitor control members 8 and the unidirectional conducting devices 25 and 26 due to the unidirectional magnetization of the saturable inductive devices l3 and I4. Consequently, the inductances 23 and 24 limit the value of the negative voltages impressed on the immersion-ignitor control members 8 through the circuits including devices 25 and 26. In order that the current transmitted to control members 8 be unidirectionahl connect in series relation therewith unidirectional conducting devices 25 and 29. Suitable current limiting or controlling resistances 21 and 28 may be con-.

nected in series relation with the unidirectional conducting devices. The resistances 21 and 28 also serve as a means for raising the potential of the relieving anodes l immediately upon the establishment of cathode spots, thereby causin the transfer of the excitation current to the relieving anodes 19..

I provide suitable means for impressing on the control baiiies or electrodes 9 voltages which not only serve to prevent theoccurrence of arc-backs within the electric discharge devices 4 and 5 but also serve to assist in the establishment of arc discharges between the cathodes l and the anodes 8 at the desired instants during the respective positive half cycles or applied anode-cathode voltage. More particularly,- I provide connections, which may include resistances 29 and 38, between the control electrodes 9 and the excitation circuits -H and I2. I have found that the control electrodes 9 may be connected to the common junctures 3| and 32 of windings IS, IS and resistances 2|, 22, respectively. -In this manner, means are provided for impressing on the control electrodes 9 negative voltages during the portions of Y the cycle when it is desired to maintain the elec-' tric discharge devicesnonconducting.

The excitation circuits H and I 2 may be energized from a suitable source of alternating current, and where it is desired to obtain a predetermined phase displacement between the voltages of peaked wave form and the anode-cathode voltage, I may employ a polyphase alternatin current circuit 33 which ener izes a transformer 34 through a phase shifting device or means, such as a capacitance 35 and a resistance 35, connected in the manner shown. It will be understood by those skilledin the art that this connection of elements afiords a ready arrangement for displacing the output voltage of transformer 34 relative to the anode-cathode voltage of the electric discharge devices.

The operation of the embodiment of my invention shown in Fig. 1 will be explained by considering the system when it is operating as a biphase rectifier to energize the direct current load circuit l. The electric discharge devices 4 and I conduct current alternately and the magnitude The operation of the arrangement of Fig. 1 may be more fully explained by referring to the characteristics shown in Fig. 2. Curve A represents the general nature of the voltage of peaked wave form produced by each of the excitation circuits i l and I 2 and may be employed to represent the voltage produced by excitation circuit H and which is supplied to electric discharge device 4.

Each of the excitation circuits II and I2 producesonly one pulse oi positive voltage during each cycle of the anode-cathode voltage supplied to the respective associated electric discharge devices 4 and 5. Curve B represents the anodecathode voltage of electric discharge device 4. At time a an impulse of current of peaked wave form is transmitted to immerslon-igm'tor control member 8, and at a time 11, immediately subsequent, upon the establishment of an arc discharge the excitation current is transferred to the relieving anode 10 to assure the maintenance of an arc discharge. Due to the connection including resistance 29, it will be observed that the potential impressed on control electrode 9 is of substantially the same wave form as curve A, and that the potential of this electrode serves to initiate and maintain the are discharge between the cathode and the anode 8. At a subsequent time, such as time 0, due to the reversal of the voltage produced by transformer 34, the inductive device 13 becomes desaturated and the voltage progresses to its negative portion. During the time cd, the voltage produced by. excitation circuit ii is negative, and durin a substantial portion of this interval it is desired to maintain the discharge device 4 nonconducting inasmuch as the electric discharge device 5 is intended to conduct current during the greater portion of this positive half cycle of applied anode-cathode voltage. A

' negative voltage is impressed on control electrode 9 from the excitation circuit it during the negative half cycles of the voltage supplied to the anode-cathode circuit of electric valve means 4. This will be appreciated by referring to curve A considered in conjimction with curve 28. Furthermore, it will be noted that during the latter portion of the positive half cycle of voltage applied to electric discharge device 4, the voltage impressed on control electrode 9 is negative, becoming negative at time. 0. However, the electrode 9 has performed its desired function or assistin in the propagation of the arc discharge from the cathode I to the'anode 6, thereby controlling the time of initiation 01' current flow between the anode and the cathode. The negative potential impressed on control electrode 9, and the characteristics of the circuit connected thereto including resistance 29, may be such that the control electrode 9 does not materially interfere with the flow of currentbetwee'n the cathode and the anode during the positive halt cycle of anodecathode voltage, but efiects rapid delonization of the medium during the negative or inverse half.

cycle of anode-cathode voltage after the current has been commutated to electric discharge device 5. In this manner, it will be readily appreciated that the control electrode 9, by virtue of its negative biasingpotential, serves to effect rapid deenergization of the medium within the electric discharge device 4 at the end of its conducting interval, and also prevents the establishment (if an arc-back during the inverse or' negative half cycle of applied anode-cathode voltage.

The phase of the voltages of peaked wave form produced by excitation circuits il and l2, and hence the magnitude of the voltage impressed across the load circuit I, may be controlled'by means of the resistance 20. Adjustment or control of resistance 20 controls the magnitude of the current transmitted to windings l1 and I8 and, hence, determines the magnetization oi. the'saturable devices l3 and I4. In this manner, the

times at which the devices l3 and I4 become sat-' urated during the respective half cycles oi. anode voltage applied to electric discharge devices 4 and 5 are controlled and, consequently, the phase po. sition of the voltages of peaked wave form is determined.

While I have shown and described my invention as applied to a particular system of connections .and as embodying various devices diagrammatcomprising an electric discharge device of the type employing an ionizable medium capable of supporting an arc discharge and including an anode, a cathode, an immersion-ignitor control member associated with said cathode and a control electrode in the vicinity of saidanode and capable of controlling the initiationof discharge between said anode and cathode, an excitation circuit for energizing said control member to render said electric discharge device conducting during a predetermined interval of each cycle of voltage of said alternating current circuit and including a saturable inductive device for producing a periodic voltage of peaked wave form having positive portions of greater magnitude and shorter duration thanthe negative portions, and means for impressing on said control electrode during each cycle of anode voltage said periodic voltage of peaked wave form so that a negative voltage exists thereon during the' latter portion of each conducting period and the entire nonconducting period of said electric discharge device and comprising a connection between said control elec- 1 trode and said excitation circuit.

2. In combination, an alternating current circuit, a direct current circuit, electric translating apparatus connected between said circuits and comprising an electric discharge device of the type employing an ionizable medium capable of supporting an arc discharge and including an anode, a athode, an immersion-ignitor control member associated with said cathode and a control electrode in the vicinity of said anode and capable of controlling the initiation of discharge between said anode and cathode, an excitation 3. In combination, an alternating current circuit, a direct current circuit, electric translating apparatus connected between said circuits and comprising an electric discharge device of the type employing an ionizable medium capable of supporting an arc discharge and including an anode, a cathode, an immersion-ignitor-control member associated with said cathode and a control electrode in the vicinity of said anode, an excitation circuit for energizing said control member to render said electric discharge device conducting during a predetermined interval of each cycle of voltage of said alternating current circuit and including a saturable inductive device and an impedance for producing a periodic voltage of peaked wave form having positive portions of greater magnitude and shorter durationthan the negative portions, andarc-back prevention means comprising a resistance connected to said excitation circuit for impressing the negative portion of said periodic voltage on said control electrode during the, latter portion of each conducting period and the entire nonconducting interval of said electric discharge device for each cycle of anode voltage.

4. In combination, an alternating current circuit, a direct current circuit, electric translating apparatus connected between said circuits and comprising an electric discharge device of the type employing an ionizable medium capable of supporting an arc discharge and including an anode, a cathode, an immersion-ignitor control member associated with said cathode, a control electrode in the vicinity of said anode and a relieving anode, an excitation circuit for energizing said control member to render said electric discharge device conducting during a predetermined interval of time during each cycle of voltage of said alternating current circuit and including a saturable inductive device for producing a periodic voltage of peaked wave form having positive portions of greater magnitude and shorter duration than the negative portions, means for impressing on said control electrode a negative voltage during the nonconducting period of said 5 electric discharge device and comprising a connection between said control electrode and said excitation circuit, and means for connecting said relieving anode to said excitation circuit to effect transfer of the excitation current from said circuit for energizing said control member to render said electric discharge device conducting during a predetermined interval of each cycle of voltage of said alternating current circuit and including a saturable inductive dtvice and an impedance for producing a periodic voltage of peaked; -wave form having positive portions of greater magnitude and shorter duration than the negative portions, and means including a resistance for connecting said control electrode to said excitation circuit at a point therein to impress upon said control electrode an alternating voltage hav ing a wave form corresponding to the voltage impressed upon said control member.

control member to said relieving a'node as soon as an arc discharge is established within said electric discharge device.

5. In combination, an alternating current circuit, a direct current circuit, electric translating apparatus connected between said circuits and comprising an electric disharge device of the type employing an ionizable medium capable of sup-.

porting an arc discharge and including an anode,

a cathode, an immersion-ignitor control member associated with said cathode, an auxiliary anode and a control electrode in the vicinity of said anode, an excitation source including means for supplying current to said immersion-ignitor control member to ionize said medium and means for impressing on said control electrode a potentialfrom said excitation source to control the conduction of current between said cathode and said anode, and means for connecting said auxiliary anode to said excitation source.

6.- In combination, an alternating current circuit, a direct current circuit, electric translating apparatus connected between said circuits and comprising an electric discharge device of the type employing an ionizable medium capable of supporting an arc discharge and including an energized from said alternating current circuit.

' said electric discharge device being of the type trode a potential to assist in the propagation of t the arc discharge from said cathode to said anode occasioned by the energization of said immersionignitor control member, and means for connecting said auxiliary anode to said excitation source.

7. In combination, an alternating current circuit, a direct current circuit, electric translating apparatus connected between said circuits and comprising an electric discharge device of the type employingan ionizable medium capable of supporting an arc discharge and including an anode, a cathode,.an immersion-ignitor control member associated with said cathode, an auxiliary anode and a control electrode in the vicinity of said anode, an excitation source including means for transmitting impulses of energizing current to said immersion-ignitor' control member and forionizing said medium and means energized from said excitation source for impressing on said control electrode a potential to control the time of initiation of current flow between said cathode and said anode, and means for connecting said auxiliary anode to said excitation source so that upon ionization of said medium the greater portion of the excitation current to said immersionignitor control member is transferred to said auxiliary anode.

8. In combination, an alternating current circuit, an electric discharge device connected to be employing an ionizable medium capable of supporting an arc discharge and including an'anode, a cathode, an ignition control member associated with said cathode, and a control electrode in the vicinity of said anode, an excitation means connected to energize said ignition control member for rendering such electric discharge device in a conductive state, and means for impressing upon said control electrode a negative voltage during the latter portion of the conducting period of said anode for causing rapid deionization of said ionizable medium at the end of the conducting period of said anode.

9. In combination, an alternating current circult, an electric discharge device connected to be energized from said alternating current circuit, said electric discharge device being of the type employing an ionizable medium capable of supporting an arc discharge and including an anode, a cathode, an ignition control member associated with said cathode, and a control electrode in the vicinity of said anode, an excitation means connected to energize said ignition control member for rendering such electric discharge device in a conductive state, and a source of excitation including a saturable inductive device for producing a periodic voltage of peaked wave form having positive portions of greater magnitude and shorter duration than the negative portions connected to energize said control electrode for impressing thereon the negative portion of said periodic voltage prior to the cessation of current in its associated anode.

LYSLE W. MORTON. 

